Nicotinic acetylcholine receptors (nAChRs) are widely distributed in the central and peripheral nervous systems, controlling peripheral voluntary motor, autonomic and central nervous system functions. Since they are found in abundance in presynaptic locations in the CNS, they can control the release of other transmitters. Therefore, they have diverse modulatory functions and are candidate targets for neurologic disorders of development, schizophrenia and autism, and the aging process, Parkinsonism and the Alzheimer dementias,ref 1-8.
Structurally, nAChRs are members of Cys-loop ligand-gated ion channel (LGIC) superfamily, which are composed of five transmembrane spanning subunits, assembled surrounding a centrosymmetric ion pore.9 There are at least 12 distinct neuronal subunits (α2-α10 and β2-β4) characterized in mammalian and avian systems.9,10 The structure of these pentameric receptors is divided into three domains: the N-terminal extracellular, transmembrane, and intracellular domains. Assembly of nAChRs is specific for certain subunit partnerships, and can be categorized in two major assemblies: hetero-pentameric and homo-pentameric. Differences in subunit combinations and localization lead to their functional and pharmacological variances.9,11,12 The orthosteric ligand binding pocket is located at the interface between a principal (alpha) and a complementary subunit in the extracellular domain.9,13 
The α7-nAChR is unique in being homomeric with identical binding sites formed between its principal, C loop containing face and the opposing face of the neighbor. The α7-nAChR is one of the major subtypes localized in cerebral cortex and hippocampus,12 which are the brain areas accounting for memory and cognition process, resulting in a concerted attempt to discover agonist compounds for this subtype of nAChRs. Accordingly, selective α7-nAChR agonists would be very useful for treating conditions involving memory and cognition processes.
Nicotinic receptors that are stimulated by acetylcholine have long been known to modulate neurotransmission in the Central Nervous System by influencing the release of other transmitters or acetylcholine itself from presynaptic sites. Such release relates to transient improvements in cognition, reinforcement of reward, and memory enhancement. The alpha-7 receptor is a prime candidate for influencing cognitive activity and information retention in the form of short term memory. Several disorders of nervous system development and incurring in the ageing process are linked to nicotinic receptor activity. Since there is plethora of nicotinic receptor subtypes, selectivity for subtype becomes critical for achieving the pharmacological action and specificity and for minimizing side effects.